1. Field of the Invention
The present invention relates to an optical data recorder device for a lens-fitted photo film unit. More particularly, the present invention relates to an optical data recorder device, incorporated in a lens-fitted photo film unit, and reliably capable of optical recording of optical data or dot indicia to photo film.
2. Description Related to the Prior Art
There is a lens-fitted photo film unit widely sold and used by many users. The lens-fitted photo film unit is pre-loaded with photo film, and incorporates a shutter mechanism, a photo film winding mechanism and a taking lens, all of which are simply constructed. Examples of the lens-fitted photo film unit include a type in which an electronic flash is built in. This type is specifically usable with convenience in photographing a dark or indoor field of view.
Also there is a system of providing photographic prints produced at plural aspect ratios selectably predetermined for increasing variety in enjoyment of photography. There are C, H and P printing sizes as examples of the aspect ratio of the photographic print. The C printing size is 89.times.127 mm, and used as the full-size, which is the most widely used format in the conventional photography. The H printing size is 89.times.157 mm, and determined similar to the aspect ratio of a display format of high-definition television (HDTV). The P printing size is 89.times.252 mm, and determined substantially two times as long as the C printing size in its longitudinal direction.
To obtain photographic prints different in the aspect ratio from a single strip of the photo film, there is a suggested method in which all imaging frames are created on the photo film at a common size. Optical data is recorded or imprinted to the photo film in a marginal region outside an effective exposure region for designating the aspect ratio of the photographic print intended for the imaging frame by the user. The optical data is hereinafter referred as print aspect ratio (PAR) indicia. In the course of producing the photographic print, the PAR indicia is detected to read the aspect ratio, for using the aspect ratio or a printing range in the printing operation of the imaging frame.
In a camera capable of photographically recording the optical data such as an exposure-taking date or the PAR indicia, a light-emitting element such as light-emitting diode (LED) is incorporated. The LED is driven in synchronism with movement of the shutter mechanism, to record the optical data to the photo film. The LED is typically inexpensive, has a long life, is stable in light emission, and is rapid in response.
The LED has a threshold voltage of about 2 volts as a minimum voltage to emit light. The LED requires voltage of 3 volts or more to illuminate stably. However a battery accommodated in the lens-fitted photo film unit of the flash built-in type or an inexpensive compact camera has electromotive force of 1.5 volts or so. It is impossible to apply the voltage of the battery directly to the LED.
U.S. Pat. No. 5,784,658 (corresponding to JP-A 8-248572) suggests a flash built-in type of the lens-fitted photo film unit in which the LED is driven to illuminate by a combination of a flash circuit and the battery as a power source having electromotive force of 1.5 volts.
In U.S. Pat. No. 5,784,658 (corresponding to JP-A 8-248572), a trigger switch for triggering emission of flash light is turned on in response to movement of the shutter mechanism to open fully. While the trigger switch is turned on, a blocking oscillator is operated. The blocking oscillator is constituted by an oscillation transistor and an oscillation transformer. Pulsed voltage is derived from a primary winding of the oscillation transformer. The pulsed voltage has a peak of for example 6 volts. The pulsed voltage is applied to the LED to emit light. The time during which the trigger switch is turned on is longer than a period of oscillation of the blocking oscillator. The LED emit light for a plurality of times while the trigger switch is turned on, to expose a position of the photo film to provide it with the PAR indicia.
As the trigger switch is a mechanical switch turned on in synchronism with operation of the shutter mechanism, the trigger switch is likely to have irregularity in the time during which the trigger switch is turned on. The number of times of light emission of the LED is changeable to vary an exposure amount of the optical data. Excess and shortage is likely to occur in the exposure amount of the optical data. Although the time of turning on the trigger switch is longer than the oscillation period of the blocking oscillator, it is somewhat short and insufficient in view of obtaining a light amount for exposing the PAR indicia on the photo film. The exposure amount of the optical data cannot be obtained sufficiently. In utilizing the PAR indicia as the optical data, it is likely that failure occurs in the operation of reading the PAR indicia in the course of producing the photographic print.